Radiographic developer compositions are well-known in the art. The processing of silver halide photographic materials is performed by a multiple step sequence consisting of development, stopping, fixing and washing steps.
The development step is conventionally undertaken with an aqueous alkaline developer composition containing a developer such as hydroquinone and/or other well-known developing agents.
More specifically, the exposure of a silver halide emulsion to radiation to which the emulsion is sensitized produced a latent image in the silver halide grains of the emulsion. The latent image is developed by immersion of the exposed emulsion in an aqueous developing solution that contains a reducing agent (or developer). The hydroquinone or other suitable developer material serves to reduce the exposed silver halide grains to yield the developed photographic image.
Exemplary hydroquinone-based developer compositions are disclosed in, for example, U.S. Pat. Nos. 2,893,865; 3,733,199; 3,865,591; 4,046,571; 4,205,124; 4,756,990; and 4,816,384. Normally, these compositions contain relatively high levels of sulfite-based components.
Developers containing ascorbic acid and ascorbic derivatives are known from publications such as U.S. Pat. Nos. 5,090,819 and 5,147,767. These developers are subject to oxidation. The oxidation is probably due to the catalytic effect of metal ions (G. Haist "Modern Photographic Processing", John Wiley and Sons, New York, 1979.) Typically, given adequate development times, developer formulations can be made, that under ideal conditions that minimize oxidation, result in sensitometry comparable to hydroquinone-based developer formulas. However to obtain adequate upper scale density longer development times are necessary.
Films developed with a ascorbic acid developers, under rapid processing conditions such as Kodak's kwik process (45 second process cycle with development times under 15 seconds) result in developed films having lower speed, contrast and Dmax.
Development accelerators are disclosed in "Photographic Processing Chemistry", Focal Press, London, 1975). The disclosed accelerators include certain cationic wetting agents and thio compounds. Cationic wetting agents (quaternary ammonium compounds) only produce the acceleration effect on developing agents that function as negatively charged species such as developers based on hydroquinone.
Aliphatic thioethers appear to be the most useful thio compounds, especially those with acid amide groups disclosed in British Patent 1,129,085; 1965. However these compounds adversely affect developers containing ascorbic acid in that at levels necessary to obtain adequate speed or high Dmin is observed.